220-1101 Question 119
Single answerLeasesA small office uses a DHCP server to assign IPv4 addresses to employee laptops. Several users report that when they return to the office after working remotely for a few days, their laptops briefly show an APIPA address before eventually reconnecting to the corporate network. The network administrator wants to reduce address exhaustion and improve how quickly returning devices receive valid addresses without manually assigning static IPs. Which DHCP configuration change would BEST address this situation?
- A
Shorten the DHCP lease duration for the wireless scope
- B
Reserve an IP address for every laptop in the DHCP scope
- C
Disable DHCP and configure all laptops with static IP addresses
- D
Increase the subnet mask size so each client keeps its address longer
Show answer and explanation
Correct answer: A
Explanation
This question focuses on DHCP leases, a Core 1 networking topic. A DHCP lease determines how long a client may use an assigned IP address before renewal is required. In an office with laptops that frequently leave and rejoin the network, overly long leases can keep addresses unavailable even when devices are gone, contributing to scope exhaustion. A shorter lease is a common best practice for networks with transient clients, such as wireless networks, training rooms, and guest environments. APIPA addresses (169.254.x.x) can appear temporarily when a client cannot immediately obtain a valid DHCP address. According to standard DHCP behavior described in Microsoft and RFC-based documentation, lease duration directly affects address reuse, while reservations are for predictability, static addressing increases support burden, and subnet masks determine address capacity rather than lease timing.
- A. Correct.
Correct. Shortening the DHCP lease duration helps reclaim addresses from devices that are away from the office for extended periods. In environments with many transient or intermittently connected clients, shorter leases reduce the chance that unused addresses remain tied up, which can help prevent temporary address shortages and improve the ability of returning devices to obtain a valid lease quickly.
- B. Incorrect.
Incorrect. DHCP reservations can ensure specific devices receive the same IP address, but reserving an address for every laptop does not reduce address exhaustion. In fact, it can make address management less flexible and is unnecessary if the goal is simply to improve reuse of addresses for laptops that disconnect for days at a time.
- C. Incorrect.
Incorrect. Replacing DHCP with static IP addressing would significantly increase administrative overhead and does not scale well for mobile laptops. It also does not solve the underlying issue of efficient address reuse in a dynamic environment. DHCP is the appropriate solution for client devices that frequently join and leave the network.
- D. Incorrect.
Incorrect. Changing the subnet mask affects the number of available addresses in the subnet, not how long clients keep leased addresses. The phrase 'so each client keeps its address longer' confuses subnet sizing with DHCP lease behavior. Lease duration is controlled by DHCP settings, not by the subnet mask.